CROSS REFERENCE TO RELATED APPLICATION
This Application claims the benefit of U.S. Provisional Application Ser. No. 61/005,065 filed Nov. 30, 2007 and entitled “Compositions for Applying to Honeycomb Bodies”.
The present invention relates to the manufacture of porous ceramic honeycomb bodies and, more particularly, to improved compositions and processes for sealing selected channels of porous ceramic honeycombs to form porous ceramic wall-flow filters therefrom.
- Top of Page
Ceramic wall flow filters are finding widening use for the removal of particulate pollutants from diesel or other combustion engine exhaust streams. A number of different approaches for manufacturing such filters from channeled honeycomb structures formed of porous ceramics are known. The most widespread approach is to position cured plugs of sealing material at the ends of alternate channels of such structures which can block direct fluid flow through the channels and force the fluid stream through the porous channel walls of the honeycombs before exiting the filter. The particulate filters used in diesel engine applications are typically formed from inorganic material systems, chosen to provide excellent thermal shock resistance, low engine back-pressure, and acceptable durability in use. The most common filter compositions are based on silicon carbide, aluminum titanate and cordierite. Filter geometries are designed to minimize engine back-pressure and maximize filtration surface area per unit volume. Illustrative of this approach is U.S. Pat. No. 6,809,139, which describes the use of sealing materials comprising cordierite-forming (MgO—Al2O3—SiO2) ceramic powder blends and thermosetting or thermoplastic binder systems to form such plugs.
Diesel particulate filters typically consist of a parallel array of channels with every other channel on each face sealed in a checkered pattern such that exhaust gases from the engine would have to pass through the walls of the channels in order to exit the filter. Filters of this configuration are typically formed by extruding a matrix that makes up the array of parallel channels and then sealing or “plugging” every other channel with a sealant in a secondary processing step.
- Top of Page
Aspects of the present invention provide improved compositions for applying to honeycomb bodies. The compositions can be applied as plugging compositions for forming ceramic wall flow filters. Alternatively, the compositions of the present invention can be applied to at least a portion of a honeycomb body as an after applied artificial skin coating. Still further, the composition of the instant invention can also be utilized as segment cements for joining two or more honeycomb bodies together. According to embodiments of the invention, the compositions can be sintered and ceramed at temperatures less than or equal to 1000° C. and may form a highly crystalline, durable, relatively low thermal expansion ceramic material with a relatively high melting point.
In one broad aspect, the present invention provides a composition for applying to a honeycomb body. According to some embodiments, the composition according to this aspect comprises an inorganic powder batch composition comprising a cordierite forming glass powder and a liquid vehicle. Further, the composition can be sintered and ceramed at a temperature T<950° C. to provide a ceramed crystalline phase cordierite composition having a coefficient of thermal expansion (CTE)≦25×10−7/° C.
In other embodiments according to this aspect, the composition comprises an inorganic powder batch composition comprising a cordierite forming glass powder that is at least substantially free of manganese. For example, in some embodiments, the cordierite forming glass powder consists on an oxide percent basis of 51% to 54% SiO2; 13% to 18% MgO; and 28% to 35% Al2O3. The compositions further comprise an organic binder; and a liquid vehicle. According to embodiments, the composition can be sintered and ceramed at a temperature T≦1000° C. to provide a ceramed crystalline phase cordierite composition having a coefficient of thermal expansion (CTE)≦25×10−7/° C.
In still another broad aspect, the present invention provides a method for manufacturing a porous ceramic wall flow filter. The method according to this aspect comprises first providing a honeycomb structure defining a plurality of cell channels bounded by channel walls that extend longitudinally from an upstream inlet end to a downstream outlet end. An end portion of at least one predetermined cell channel is selectively plugged with a composition as described herein. The selectively plugged honeycomb body can then be fired at a temperature in the range of from 800° C. to 1000° C. for a period of time sufficient to form a crystalline ceramic plug in the at least one selectively plugged channel.
In still another broad aspect, the present invention provides a porous ceramic wall flow filters manufactured from the processes and plugging compositions described herein.
Additional embodiments of the invention will be set forth, in part, in the detailed description, and any claims which follow, and in part will be derived from the detailed description, or can be learned by practice of the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
- Top of Page
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain embodiments of the instant invention and together with the description, serve to explain, without limitation, the principles of the invention.
FIG. 1 is an isometric view of porous honeycomb substrate according to embodiments of the invention.
FIG. 2a and FIG. 2b illustrate shrinkage dilatometry data for example compositions 13 through 17.
FIG. 3a and FIG. 3b illustrate a dL/dT versus temperature curve for the cordierite grog/glass mixtures of example compositions 13 through 17.
FIG. 4a and FIG. 4b illustrate shrinkage dilatometry data for an exemplary plugging composition comprising a cordierite grog/glass mixture wherein the ratio of grog to glass is 1:1.
FIG. 5a and FIG. 5b illustrate shrinkage dilatometry data for a first comparative plugging composition comprising cordierite grog in the absence of powdered glass.
FIG. 6a and FIG. 6b illustrate shrinkage dilatometry data for a second comparative plugging composition comprising a cordierite grog in the absence of powdered glass.
- Top of Page
The present invention can be understood more readily by reference to the following detailed description, drawings, examples, and claims, and their previous and following description. However, before the present compositions, articles, devices, and methods are disclosed and described, it is to be understood that this invention is not limited to the specific compositions, articles, devices, and methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
The following description of the invention is provided as an enabling teaching of the invention in its best currently known embodiments. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various embodiments of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof.
Disclosed are materials, compounds, compositions, and components that can be used for, can be used in conjunction with, can be used in preparation for, or are products of the disclosed method and compositions. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds may not be explicitly disclosed, each is specifically contemplated and described herein. Thus, if a class of substituents A, B, and C are disclosed as well as a class of substituents D, E, and F and an example of a combination embodiment, A-D is disclosed, then each is individually and collectively contemplated. Thus, in this example, each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C—F are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D. Likewise, any subset or combination of these is also specifically contemplated and disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D. This concept applies to all embodiments of this disclosure including, but not limited to any components of the compositions and steps in methods of making and using the disclosed compositions. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods, and that each such combination is specifically contemplated and should be considered disclosed.
In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:
As used herein, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a “component” includes embodiments having two or more such components, unless the context clearly indicates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not. For example, the phrase “optional component” means that the component can or can not be present and that the description includes both embodiments of the invention including and excluding the component.
Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.